Take any two digit number, for example 58. What do you have to do to reverse the order of the digits? Can you find a rule for reversing the order of digits for any two digit number?

Chocolate Maths

Stage: 3 Challenge Level:

Thank you to Gareth Matthews, Llantwit
Major Comprehensive School for this solution. Jenny Cook, age 15,
The Mount School York, Andrei Lazanu, age 12, School 205,
Bucharest, Romania and Clement Goh, age 13, from River Valley High
School, Singapore all sent good solutions.

I used algebra to get my answer.

The problem

The solution

My calculation

First of all, pick the number of times a week that you eat
chocolate.

A

7

Multiply this number by 2 (just to be bold).

2A

14

Add 5 (for Sunday).

2A+5

19

Multiply it by 50.

100A+250
This multiplies the original number by 100 and adds 250

950

Add 1750, then the last two digits of the year you last had a
birthday.

100A+2000+ab

2709

Now subtract the four digit year that you were born (if you
remember).

100A +2000+ab-cdef
Subtracting the year i was born (cdef) from the year I
last had a birthday (20ab) gives my age. 100A puts the number A in
the hundreds place.

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